Circuit/System Testing

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

Ignition ON, with a scan tool perform the display test for the instrument panel cluster (IPC) and observe the lights on indicator.

Dimmer Switch Circuit Test

If the lights on indicator does not illuminate during the test or remains illuminated at all times, replace the IPC.
If the lights on indicator illuminates during the test, replace the BCM.